This application claims the priority of German application 198 49 027.5, filed in Germany on Oct. 23, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method and system for triggering an airbag provided with a gas generator controlled by a power control device.
Instead of airbags that have a gas generator that can be triggered once, preferably pyrotechnically, airbags are increasingly coming into use with gas generators whose performance can be controlled. The variation of the power of the gas generator serves to adapt the effect of the airbag to the seriousness of an individual accident. In particular, gas generators are used that can be triggered in stages. The performance of the gas generator over time can be varied by the time interval between the triggering stages.
A goal of the invention is to provide a method and system for triggering an airbag which ensures a protective effect of the airbag that is better adapted to a given accident or type of accident.
The invention achieves this goal by providing that a coolant is introduced as desired into the gas emerging from the gas generator in order to reduce the power developed by the gas generator.
In addition to or alternatively to the possibilities provided by the time curve of the power control unit that influences power development, additional variation of the power developed by the airbag is made possible by the invention. The maximum pressure can be varied by using a coolant. This applies both to the magnitude of the maximum pressure as well as the point in time at which this pressure maximum is reached. Power can be controlled for example in such fashion that excessive power development by the gas generator is compensated. In certain types of accidents that require less power to be generated by the airbag, the power can be adjusted to the requirements. For this purpose, power can be varied for example for an airbag that can be triggered in stages in such fashion that the beginning and/or end of the introduction of the coolant is varied accordingly. In addition, the action of the gas generator can be weakened by varying the quantity of coolant. In particular, the combination of a gas generator that can be triggered in stages with the possibility of varying the time intervals of the stages and with the influence of ambient temperature on the action of the gas generator and the variation of the coolant flow as regards beginning, duration, quantity, and change in quantity results in ideal adjustment of the action of the airbag to specific requirements.
The coolant itself can be chosen to correspond to individual requirements regarding cost, shelf life, activatability, and effectiveness. One possibility for doing this is using water as the coolant which, as it evaporates, draws heat from the environment and meets these requirements in an ideal fashion.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.